The present invention relates to a method for making a beam from a metal sheet. In particular, the present invention relates to a method for making a tubular beam from a sheet wherein one or both of the edges of the sheet are split so as to form flanges, the flanges are then bent so as to provide one or more tubular portions along the edges of the beam.
Elongated metal beams are used throughout the frame of a motor vehicle. One such beam, for example, is the intrusion beam used in motor vehicle doors. In constructing such beams, special attention must be paid to ensuring that the beam is sufficiently rigid to withstand the loads and impacts applied to it. However, the beam should also be kept lightweight enough to ensure that the resulting vehicle is fuel efficient and easy to handle. To this end, vehicle frame manufacturers have typically utilized I-beams and stamped or roll-formed metal beams. The common desired feature among all of these known beam or frame members is that they have a relatively high resistance to bending and torsion without unnecessarily adding to the overall weight of the vehicle.
While these known frame members have been viewed as satisfactory, it would be desirable to provide an alternative, cost-effective and relatively simple method for providing a frame member that achieves the desired bending and torsional resistance and weight characteristics for a vehicle frame.
It is therefore an object of the present invention to provide an alternative method for making a lightweight beam having high resistance to deformation.
According to the method of the present invention, a metal sheet is provided. The metal sheet has first and second side edges extending longitudinally along opposing sides of the metal sheet and first and second generally parallel opposing face surfaces provided between the first and second side edges. First and second integral flanges are formed from a portion of the metal sheet by splitting the portion of the metal sheet at one of the first and second side edges while leaving a portion of the metal sheet unsplit. Then the first and second flanges are bent so as to provide the metal sheet with a tubular portion extending along one side of and integrally formed with the unsplit portion. Then, the first and second flanges are fixed against movement relative to one another.
According to the method of the present invention, the thickness of the metal sheet may be split in the manner described above by using a splitting tool. The manner in which the flanges are bent may be in one of two ways. The first way is to bend the flanges so that the free ends are moved towards the unsplit portion of the sheet and then fix the free ends of the flanges to the first and second surfaces of the metal sheet by welding or the like. As a result, the flanges will form two tubular portions. Where both edges on opposite sides of the metal sheet are split, two tubular portions are formed on both sides of the web, with a central unsplit web extending therebetween. The second way to bend the flanges is to bring the free ends thereof into engagement with one another and then secure the free ends together by welding of the likes so as to provide the metal sheet with a single tubular portion. Where both edges on opposite sides of the metal sheet are split, a single tubular portion is formed on both sides of the web, with the web extending therebetween.
While the present invention contemplates that the splitting can be accomplished on only one side of the sheet metal, leaving a tubular portion (either single or double tubular portion) on one side of the unsplit portion of the metal sheet, in the preferred embodiment, both of the opposite longitudinal edges are split to provide tubular portions (either single or double) on opposite side of an unsplit portion therebetween. It can be appreciated that the method of the present invention is a simple and inexpensive way of forming a tubular beam from a metal sheet. The tubular beam resulting from the method of the present invention may be used in the frame of the motor vehicle or may be used at any other point in the vehicle where the use of such a member (either straight or bent) would be desired. For example, the beam could be used in a vehicle door as an intrusion beam or in a vehicle roof for support. Also, the method of the present invention may be applied to other fields outside the automotive industry.